The present application is generally related to a system, instruments and methods for monitoring the flight of an aircraft and, more particularly, to an advanced system, apparatus and methods for monitoring the flight of the aircraft based on a determination of centripetal acceleration.
In one aspect of the prior art, modern aircraft and other vehicles such as boats and ships often include one or more GPS (Global Positioning System) receivers for purposes of monitoring the progress and movement of a craft. Applicant recognizes, however, that a GPS receiver is ineffective in terms of characterizing movement of an ambient that supports the moving craft such as, for example, air or water. Using the example of an aircraft, it can be critical to know the airspeed of the aircraft, especially in windy conditions, for purposes of avoiding operation of the aircraft beyond its design limits. As will be further discussed below, attempting to maintain a constant GPS groundspeed of an aircraft subject to a tail wind can result in exceeding the airspeed design limits of the aircraft when turning from downwind to upwind.
One approach for avoiding airspeed design limitations resides in providing an airspeed sensor such as, for example, a pitot tube. While such sensors are generally effective, it should be appreciated that the cost for the addition of such a sensor is not trivial. Further, airspeed sensors can be subject to failure. For example, a pitot tube can be subject to icing over or becoming clogged with other foreign material. Thus, even in an aircraft that includes an airspeed sensor, Applicants recognize that an additional system for independently determining airspeed can be valuable.
One recent approach for determining airspeed without using an airspeed sensor is described in a posting entitled Wind estimation without an airspeed sensor(http://diydrones.com/forum/topics/wind-estimation-without-an, dated Jan. 29, 2010). This approach, however, must utilize a pair of GPS readings in conjunction with a direction cosine matrix for purposes of estimating the airspeed. It should be appreciated that the formation of the cosine matrix is not trivial and requires measurements along all three axes of rotation. In a typical implementation, triaxial rate gyros or triaxial attitude gyros and triaxial accelerometers, and triaxial magnetometers are needed in conjunction with the GPS for slaving the rate gyros. Triaxial rate gyros and triaxial accelerometers are not normally included as standard equipment in an aircraft's equipment.
In another aspect of the prior art, a gyro is sometimes used to augment a magnetic compass to form what can be referred to as a slaved gyro. As will be further discussed, the reference for this slaved gyro should be the Earth's gravitational vector, so that a turn is represented by the slaved gyro in the Earth's gravitational axis system. Unfortunately, however, centripetal acceleration during a turn produces an acceleration that adds to the gravitational acceleration when an aircraft makes a coordinated turn such that the total acceleration is towards the floor of the aircraft. Applicant recognizes that slaving a gyro to this apparent acceleration can be problematic since the gyro will tend to shift to an axis as a reference which is perpendicular to the floor of the aircraft in a turn, if the aircraft executes a turn of sufficiently long time duration unless the centripetal acceleration factor is compensated.
The foregoing examples of the related art and limitations related therewith are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the drawings.